this technology was ever offered. The idea of four-wheel steering has been revisited in an electric vehicle ROboMObil of the German Aerospace Center. The vehicle stops in front of an empty parking spot and re-orients its four wheels in the perpendicular direction (leaving rubber marks on the road) to prepare for subsequent sideward motion. In 2004, a group of Linköping University students working with Volvo developed a project Evolve. The Evolve car can automatically perform parallel parking by using sensors and a computer to control steering, acceleration and braking of Volvo S60. An automatic parking system uses various methods to detect objects around the vehicle. Sensors installed on the front and rear bumpers can act as both a transmitter and a receiver. These sensors emit a signal that will be reflected back when it encounters an obstacle near the vehicle. Then, the car will use the time of flight to determine the position of the obstacle. Other systems use cameras, e.g. Omniview technology, or radars to detect obstacles and measure the parking space size and distance from the roadside. An automatic parking system has been shown to improve comfort and safety by reducing the level of stress people feel when manual steering for parallel parking and garage parking maneuvers. Commercial systems In 2003, Toyota began to sell their Japanese Prius hybrid vehicle with an automatic parallel parking capability offered as an option named Intelligent Parking Assist. In 2006, Lexus added a self-parking system to the redesigned Lexus LS sedan; it parallel parks as well as angle parks. In 2009, Ford introduced their Active Park Assist beginning with their Lincoln models; it does parallel parking. In 2010, BMW introduced a system called "parking assistant" on the redesigned 5 Series to perform parallel parking. Up to 2012, automatic parking systems were being developed by several automobile manufacturers. Ford and Lincoln offered active park assist on Ford Focus, Fusion, Escape, Explorer, and Flex and Lincoln MKS and MKT. Toyota and Lexus had advanced parking assistant on Toyota Prius V Five and Lexus LS460 and LS460 L. BMW all-new sixth-generation 3 Series used a system called parking assistant. Audi had a parking assistance system on the Audi A6. Mercedes-Benz also offered parktronic on their C-Class, CLS-Class Coupe, M-Class SUV, E-Class, S-Class, GL350, GL450 SUV (standard on the GL550), and R-Class in different prices. Jeep introduced an automatic parallel and perpendicular parking system, called ParkSense,